Editing Symbiosis (section)

=== Amensalism ===

[[File:Black Walnut middle.JPG|right|thumb|The [[black walnut]] secretes a chemical from its roots that harms neighboring plants, an example of [[antagonism (phytopathology)|antagonism]].]]

Amensalism is a non-symbiotic, asymmetric interaction where one species is harmed or killed by the other, and one is unaffected by the other.<ref>Toepfer, G. "Amensalism". In: ''BioConcepts''. [http://www.biological-concepts.com/views/search.php?term=1440 link] {{Webarchive|url=https://web.archive.org/web/20171209043914/http://www.biological-concepts.com/views/search.php?term=1440 |date=2017-12-09 }}.</ref><ref name="Willey-2013">{{cite book |last1=Willey |first1=Joanne M. |last2=Sherwood |first2=Linda M. |last3=Woolverton |first3=Cristopher J. |year=2013 |title=Prescott's Microbiology |edition=9th |pages=713–738 |isbn=978-0-07-751066-4}}</ref> There are two types of amensalism, competition and [[antagonism (phytopathology)|antagonism]] (or antibiosis). Competition is where a larger or stronger organism deprives a smaller or weaker one of a resource. Antagonism occurs when one organism is damaged or killed by another through a chemical secretion. An example of competition is a sapling growing under the shadow of a mature tree. The mature tree can rob the [[sapling]] of necessary sunlight and, if the mature tree is very large, it can take up rainwater and deplete soil nutrients. Throughout the process, the mature tree is unaffected by the sapling. Indeed, if the sapling dies, the mature tree gains nutrients from the decaying sapling. An example of antagonism is ''[[Juglans nigra]]'' (black walnut), secreting [[juglone]], a substance which destroys many herbaceous plants within its root zone.<ref>''Encyclopædia Britannica''. "[http://www.britannica.com/EBchecked/topic/19211/amensalism Amensalism (biology)]". Retrieved September 30, 2014.</ref>

The term ''amensalism'' is often used to describe strongly asymmetrical competitive interactions, such as between the [[Spanish Ibex|Spanish ibex]] and [[weevil]]s of the genus ''[[Timarcha]]'' which feed upon the same type of shrub. Whilst the presence of the weevil has almost no influence on food availability, the presence of ibex has an enormous detrimental effect on weevil numbers, as they consume significant quantities of plant matter and incidentally ingest the weevils upon it.<ref name="Gómez-2002">{{cite journal |last1=Gómez |first1=José M. |last2=González-Megías |first2=Adela |year=2002 |title=Asymmetrical interactions between ungulates and phytophagous insects: Being different matters |journal=Ecology |volume=83 |issue=1 |pages=203–11 |doi=10.1890/0012-9658(2002)083[0203:AIBUAP]2.0.CO;2}}</ref>